Hi,
The Dremel I used is a "Multi-Pro". I tink it's pretty much the basic model with a variable speed control. The bit is from a 249 pc accessory kit from Harbor Freight that cost about $15 or so. Working slowly, double checking that I'm using the proper code and that the scribes are accurate before I grind, I'd estimate that it takes between ten and twenty minutes a lens, not counting time for the nail polish to dry.
There's no question that the hand coding will reduce the resle value of the lenses. But I saved more than $100 per lens at the cost of a bottle of nail polish, Leica won't code a number of those lenses, and I bought the lenses to use not resell. I plan to die broke with a used up body, and feel the same about my gear. OF course, timing is the key ;-)
Regards,
Bob